An innovative optimal approach to Slotted-ALOHA random access protocol

Abstract

This work presents an innovative, adaptive and optimal approach for Slotted-ALOHA protocols in Satellite Networks. Most ALOHA random access protocols are based on the assumptions that: i) all the involved stations receive packets with the same rate and ii) the transmission probabilities, computed analytically, are the same for each station. These assumptions are too optimistic, since, in real scenarios, different sources receive traffic with different arrival rates: a classical approach leads therefore to a sub-optimal exploitation of the available resources. The proposed algorithm takes into account the arrival rate of the traffic, considered as generated by different services. The traffic model is then used to compute the (stationary) probabilities of the traffic arrival rate of the stations: each station is characterized by a finite set of arrival rates and each arrival rate is associated to a stationary probability. Then, an optimization problem is defined, aimed at obtaining the transmission probabilities which minimize the channel collisions; the innovation is that the transmission probabilities are associated to the traffic arrival rate and are different depending on the arrival rates themselves. The increased efficiency of the proposed solution with respect to the standard ALOHA approach is proved by means event-based simulations (performed with Matlab simulation tools). The work is partially based on research activities carried out in the framework of the EmerSat project funded by ASI (Italian Space Agency).